It is known to hydroform a tube by enclosing the tube in a die and then using internal pressure to expand the tube outwardly into conformance with the shape of the die.
It is often desirable that such a hydroformed tube have different characteristics, such as metal thickness or material, along its length. To that end, U.S. Pat. No. 5,333,775 Bruggemann et al, assigned to the assignee of this invention, proposed that tubes of different material, perimeter or thickness could be welded together end-to-end to form a tubular blank that could then be hydroformed.
It would be desirable to provide further improvements in the method of manufacture of hydroformed tubular structures of complex shape.